This invention relates to high-speed serial interface (“HSSI”) circuitry, and more particularly to clock circuitry for use in HSSI circuitry that can be used to support any of several different signalling protocols (e.g., as in a programmable logic device (“PLD”) that may have any of several different uses).
If the circuitry of this invention is used in a device such as a PLD, the device can be either field programmable, mask programmable, or programmable in any other way. It will be understood that terms like “PLD,” “programmable,” and the like include all of these various options. Also, terms like HSSI and HSSC are used just for convenience herein and not with the intention of limiting the invention to any rigorously defined set of possible applications or uses. Thus the invention is applicable in any context that involves an appropriate type of communication or signalling.
High-speed serial communication (“HSSC”) is becoming increasingly popular for many different communication applications. HSSC can take many forms, including (1) many industry-standard forms such as XAUI, Infiniband, Gigabit Ethernet, Packet Over SONET or POS-5, etc., and (2) any of a wide range of non-industry-standard or “custom” forms that particular users devise for their own uses. Such custom protocols often have at least some features similar to industry-standard protocols, but deviate from industry standards in other respects.
PLDs are typically designed to meet a wide range of different user needs. This is done so that a PLD can be manufactured in large quantities (and therefore at reduced unit cost) and sold to a large number of users for many different uses. There is increasing interest in using PLDs in applications involving HSSC. In keeping with the usual philosophy behind the design of PLDs (and in view of the many different HSSC protocols that are known and that can be developed), it is desirable for a PLD that may be used in HSSC applications to have considerable flexibility with regard to supporting different HSSC protocols.
Illustrative PLDs with certain HSSC capabilities are shown in Aung et al. U.S. patent application Ser. No. 09/805,843, filed Mar. 13, 2001, Lee et al. U.S. Pat. No. 6,650,140, and Venkata et al. U.S. Pat. No. 6,750,675. The PLDs shown in these references can support various HSSC protocols. But even greater flexibility in that regard would be desirable and is among the motivations for the present invention.